210 FAUNA OF SHROPSHIRE. 



their maximum size before the production of any limbs, but 

 about the time when these appear they diminish in size 

 externally, and gradually disappear. Meanwhile a fresh and 

 more complex pair of gills are being formed inside, in 

 pockets, or chambers, one on each side of the mouth. These 

 gills are arranged in tufts on four cartilaginous arches, and 

 number over a hundred on each side. When they are fully 

 formed the external gills entirely vanish. The water now 

 passes in through the mouth over the new gills and out 

 through a single tube opening on the lower face, or left side 

 of the body. These gills resemble those of fishes in their 

 function of respiration ; they differ from fishes' gills in having 

 a branched instead of laminated form, in having a single 

 outlet instead of one each side, and in having no bony gill- 

 covers. The gills in newt-tadpoles continue external till they 

 attain the adult quadrupedal form and leave the water. Soon 

 after the external gills are developed, the tadpole grows a 

 pair of limbs. [Hind-limbs if Frog or Toad ; front -limbs if a 

 Newt.] These appear first as knobs on each side of the 

 body, and steadily develop till they assume the shape of the 

 legs in the adult. The second pair of limbs is formed 

 subsequently in the same way, while simultaneously the tail 

 gradually shortens [except in Newts] , till it finally becomes a 

 mere rudiment or stump, and the animal is a perfect Frog, 

 or Toad, as the case may be. Not quite though Before 

 finally leaving its nursery the little creature has got to 

 become an air-breather, and accordingly during the process 

 of its metamorphosis it has developed inside the body true 

 lungs, which, although present before in a rudimentary solid 

 condition, only now open out and increase in size ready to 

 come into play when it leaves its native pond or ditch, and 

 starts afresh as a terrestrial and carnivorous animal. The 



